1. Field of the Invention
The present invention relates to a ratchet one-way clutch using a ratchet (pawl) as a lock mechanism, among one-way clutches used in a transmission in an automobile, a farm machine, a building machine, an industrial machine and the like, particularly, in an automatic transmission of a vehicle and having a function such as back-stop. More particularly the present invention relates to a ratchet one-way clutch having a bearing portion.
2. Related Background Art
In general, a one-way clutch used in an automatic transmission has outer and inner races which are rotated relative to each other so that torque can be transmitted only in one direction when sprag or a roller for transmitting the torque between the outer and inner races is engaged by a cam surface provided on a track face of the outer or inner race. On the other hand, the clutch is idly rotated in the other direction.
Among such one-way clutches, there is a ratchet one-way clutch having a ratchet as a torque transmitting member for transmitting the torque between the outer and inner races. The ratchet one-way clutch includes an outer race having a pocket in an inner periphery thereof, an inner race disposed in coaxial with the outer race and having a notch in an outer periphery thereof, a pawl contained in the pocket and maintaining the one-way clutch in a locking condition by fitting the pawl into the notch thereby to transmit torque between the inner and outer races, and an elastic member such as a spring for biasing the pawl toward the inner race. In recent years, development regarding compactness, weight reduction and cost reduction of part of an automobile such as an automatic transmission has been made widely, and the one-way clutch is also included in such development. To satisfy such requirement, usage of the ratchet one-way clutch has been proposed.
In the ratchet one-way clutch having the above-mentioned construction, when the one-way clutch is rotated in one direction, since the pawl is feely slid with respect to the outer periphery of the inner race, the outer and inner races are idly rotated relative to each other. Then, when the one-way clutch tried to rotate in the other direction, the pawl is fitted into the notch so that the one-way clutch becomes the locking condition.
FIG. 5 is a partial front view of a conventional ratchet one-way clutch and shows an example that a hub of the clutch is used as an outer race. The ratchet one-way clutch 101 has an inner race 102 and an outer race 122 which are disposed in coaxial with each other, and pawl 123 is provided on an inner peripheral portion of the outer race 122 and is biased by a garter spring 124. In this ratchet one-way clutch 101, when the inner race 102 and the outer race 122 are rotated relative to each other in a predetermined direction, the pawl 123 is fitted into a recess provided in the outer periphery of the inner race 102 thereby to transmit the torque, and, when the races are rotated relative to each other in a reverse direction, the clutch is idly rotated. Further, splines are provided on the inner periphery of the inner race 102 and the outer periphery of the outer race 122. Incidentally, an example of such a ratchet one-way clutch is disclosed in U.S. Pat. No. 5,853,073 in detail.
In conventional one-way clutches including the ratchet one-way clutch, in many cases, although bearings are disposed in coaxial with each other, problems regarding compactness, weight reduction and reduction in the number of parts of the automatic transmission which must satisfy recent severe requirements have still be remained.
Therefore, an object of the present invention is to provide a one-way clutch assembly which achieves compactness, weight reduction and reduction in the number of parts of an automatic transmission by constructing a ratchet one-way clutch and a bearing as a single assembly.
To achieve the above object, the present invention is characterized by a one-way clutch assembly comprising a ratchet one-way clutch portion including inner and outer races which are disposed in coaxial with each other, a pawl capable of being fitted into a recess provided in the inner or outer race to transmit torque, and a biasing member for biasing the pawl to promote the fitting, and a bearing portion disposed between the inner race and the outer race.
The bearing used in the present invention is not particularly limited and, various bearings rolling bearing such as a deep groove ball bearing, a magnet ball bearing, an angular ball bearing, a multiple line angular ball bearing, a combined angular ball bearing, a four-point contact ball bearing, an automatic centering ball bearing, a cylindrical roller bearing, a multiple line cylindrical roller bearing, a single-flanged cylindrical roller bearing, a flange-wheeled cylindrical roller bearing, a needle roller bearing, a conical roller bearing, a multiple line/multiple strand conical roller bearing, an automatic centering roller bearing, a thrust ball bearing, a centering washer thrust ball bearing, a dual thrust angular ball bearing, a thrust cylindrical roller bearing, a thrust conical roller bearing and a thrust automatic centering roller bearing may be used.
Further of course, various bearings in which phosphorus bronze, lead bronze, high lead bronze, babbit, aluminum alloy, cadmium alloy or silver plating is used as bearing alloy and bimetallic material using steel, cast iron and bronze or solid material using iron, stainless steel and special alloy such as copper alloy or iron coated by copper or lead is used as backing plate can be used. In addition, a tightly sealed bearing with a seal can be also used.
Although any material for the outer race of the ratchet one-way clutch can be used, it is preferably made of aluminum. When the outer race is made of aluminum, the weight of the one-way clutch can be reduced and the one-way clutch can be manufactured by die casting, thereby improving productivity.
The outer race of the bearing can be incorporated into the outer race of the ratchet one-way clutch, because, when the outer race of the ratchet one-way clutch is made of aluminum as mentioned above, if the aluminum portion is used as the outer race of the bearing as it is, strength may become insufficient.